MRI Final

Which component is utilized to maintain low temperatures necessary for superconductivity in MRI machines?

Cryocooler

What is a bore diameter of a typical clinical MRI magnet?

60 cm

Which of the following components of an MRI magnet functions to create a large magnetic field?

B0

What is the function of the MRI gantry?

It accommodates the patient and source/detector assemblies

What is the critical temperature for superconductivity in niobium-titanium alloys used in MRI magnets?

9 Kelvin

What units do we use to specify magnetic field homogeneity?

Parts per million (ppm)

Which type of MRI system is most often used in clinical settings today?

Superconducting electromagnet

How is the MRI system cooled to produce the high B0 field?

with cryogens

An MRI head coil is typically what type of coil?

Birdcage coil

What causes the loud thumping noise during an MRI scan?

Lorentz Force

SAR is an abbreviation for

specific absorption ratio

What produces the noise in MRI?

The gradient coils switching

Which component is often referred to as the “traffic cop” of the MRI scanner?

Sequencing system (Pulse programmer)

The objects pictured here are

RF coils

Which of the following is the most common type of magnet used to generate the B0 in clinical MRI scanners?

Superconducting magnet

Presaturation pulses can be used to

eliminate fat from an MR image

Decreasing the FOV while keeping the image matrix the same size will

increase spatial resolution

Which of the following components of an MRI magnet functions to receive the MRI signal?

RF receive coil

In a permanent magnet MRI system, which axis is vertical?

Z-axis

What material is commonly used in superconducting electromagnets for MRI?

Niobium-titanium alloy

Which of the following is NOT an advantage of permanent magnet MRI systems?

High magnetic field homogeneity

Reducing slice thickness will ___ SNR and ___ spatial resolution.

decrease; increase

In which zone is the MRI Operating Console Room typically located?

Zone 3

What is a quench in the context of superconducting MRI systems?

The loss of superconductivity in the B0 coil

Which type of MRI system produces a vertical B0 field and looks like a large C-arm?

Resistive electromagnet

Increasing the number of signal acquisitions in MRI will

increase the signal-to-noise ratio

Which component is responsible for amplifying signals in an MRI system?

RF amplifier

FOV is an abbreviation for

field of view

Which of the following components of an MRI magnet functions to help keep the main magnetic field more homogenous?

Shim coil

Why is the isocenter important in MRI imaging?

It ensures optimal patient positioning within the magnetic field

What are the three major components of a magnetic resonance imaging (MRI) system?

Magnet (Gantry), Operating console, System electronics

What is the principle advantage of a permanent MRI magnet?

Insignificant fringe field

What is the container that houses the superconducting wire and cryogens called?

Cryostat

Which of the following is NOT one of the four electrical states of matter mentioned in the document?

Plasma

What is the primary advantage of a permanent magnet MRI system?

Low fringe magnetic field

What is the most common type of magnet used in MRI systems?

Superconducting electromagnet

What is a typical field strength of a superconducting magnet?

1.5T

What is the process of gradually decreasing the current in a superconducting magnet to return it to a non-superconducting state?

Ramping Down

The SAR characterizes

the amount of heat absorbed by the patient

What is the typical weight limit for a patient on an MRI couch?

350 lbs

Which of the following is NOT a subassembly of a superconducting MRI system?

Resistive coils

How many sets of gradient coils are inside an MRI machine?

3

What is the purpose of the frequency synthesizer in an MRI system?

To generate the fundamental resonance frequency

What is the maximum magnetic field strength typically achieved by permanent magnets in whole-body MRI systems?

0.3T

What is the purpose of shim coils in an MRI system?

To make the B0 field homogeneous

What role do secondary magnets play in MRI systems?

Adjust the B0 field and create gradient magnetic fields

What is the cryogen used primarily to cool MRI magnet coils?

Liquid Helium

What is the primary role of shim coils in an MRI system?

To ensure magnetic field homogeneity

What is the geometric center of an MR magnet called?

Isocenter

Which of the following is not contained within the gantry?

control panel

What is a cryostat used for in MRI systems?

To hold superconducting wire and cryogens

What is the primary function of the primary magnets in MRI systems?

To provide a static magnetic field (B0)

Which of the following components of an MRI magnet functions to change the direction of the net magnetization vector?

RF Transmit coil

How are gradient coils utilized in an MRI system?

They create varying magnetic fields for imaging

Which type of RF receive coil can detect signals from multiple directions?

Quadrature coil

Which of the following components of an MRI magnet functions to deliberately spoil magnetic field homogeneity?

Gradient coil

What is a typical field strength of a resistive electromagnet?

0.2T

What is the term for the loss of superconductivity in the B0 coil that may occur unexpectedly?

Quench

What is the only moving part of an MRI machine?

The table

What is a major disadvantage of resistive electromagnet MRI systems?

High electric power consumption

What is the purpose of shimming a magnet?

Creating a more homogeneous magnetic field

An MRI machine’s appearance most resembles that of ____.

a CT machine

What does the term slew rate refer to?

The maximum rise of a gradient coil

What do shim coils do?

Make B0 more homogeneous

What does the RF transmit coil do?

Produces a magnetic field perpendicular to the B0

What causes aliasing?

under sampling

What does the eye use to detect light?

Rods and Cones

How does the phase-encoding gradient work in MRI?

Both B and C -It is energized as a pulse before signal reception & its amplitude is varied while its duration is fixed

What is the primary difference between regular visual images and medical images?

Medical images are of the interior body, while visual images are of the surface

What is the purpose of the 180 degree RF pulse in a spin echo sequence?

To refocus the spins

Bandwidth _____ as RF pulse duration _____.

narrows; increases

Which of the following is not a parameter that affects the pixel character in MRI?

Imaging time

Which of the following modalities typically has the best spatial resolution?

X-ray

Multislice imaging techniques help to _____.

decrease imaging time

What is the purpose of quantization or resolution in digital imaging?

All of the above- to improve the precision and dynamic range of pixel values & to reduce the effects of false contouring

Which MRI pulse sequence is best for producing T2-weighted images?

Spin echo with long TE

How does receiver bandwidth affect signal-to-noise ratio (SNR) and field of view (FOV) in MRI?

Narrower bandwidth improves SNR but reduces FOV

Which of the following is the most widely used type of pulse sequence in MRI?

Spin echo

Which of the following is used during night vision or scotopic vision?

Rods

What does the term dynamic range refer to?

The number of gray scales a system can display

How do partial saturation and inversion recovery pulse sequences differ in their effects on the spins?

Partial saturation uses a 90 degree pulse, while inversion recovery uses a 180 degree pulse

What will help improve contrast resolution the most?

An increase in SNR

What do we call the diagram that lays out the schematic of an MRI acquisition procedure?

pulse sequence

What is the purpose of the gradient coils in an MRI system?

All of the above

Which of the following is implemented before signal reception and not during the RF transmit pulse?

Phase-encoding gradient

What is the relationship between the matrix of k-space and the resulting image?

Both A and C

A radiograph is primarily what type of image?

Electron density

If the field of view (FOV) of an MRI scan is increased, what will happen to the pixel size if the matrix size stays the same?

It will increase

What is the RF pulse sequence for an inversion recovery MRI technique?

180…90…/…180…90…/…180…90…/….

What is the purpose of high-amplitude phase encoding gradients in k-space?

Both A and C

Which is not a state that MRI proton spins can exist in?

Partial equilibrium

Which of the following localizes the MRI signal?

Gradient coil

Which of the following determines slice thickness?

Slice-encoding gradient amplitude

Which of the following has the highest proton density?

CSF

Which MRI pulse sequence is best for producing proton density weighted images?

Partial saturation

What is the purpose of the sinc function in MRI?

All of the above

What is the typical resolution of an MR image?

1 lp/mm

How are the different k-space sampling methods (spiral, square spiral, interleaved spiral) processed?

Both B and C

What type of artifact appears as a “wrap around”?

Aliasing

In what units do we typically measure spatial frequency in MRI?

lp/cm